core: Fix #25 and add a unit test for CommentedConfig.clearComments()

core/src/main/java/com/electronwill/nightconfig/core/AbstractCommentedConfig.java

@@ -197,5 +197,12 @@ public void clear() {
 	@Override
 	public void clearComments() {
 		commentMap.clear();
+		// Recursively clears the comments of the subconfigs:
+		for (Object o : map.values()) {
+			if (o instanceof CommentedConfig) {
+				((CommentedConfig)o).clearComments();
+			}
+		}
+		//NB: The UnmodifiableCommentedConfigs cannot be cleared from their comments.
 	}
 }

core/src/test/java/com/electronwill/nightconfig/core/AbstractCommentedConfigTest.java

@@ -0,0 +1,48 @@
+package com.electronwill.nightconfig.core;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * @author TheElectronWill
+ */
+class AbstractCommentedConfigTest {
+
+	@Test
+	public void testClearComments() {
+		CommentedConfig config = CommentedConfig.inMemory();
+		config.set("a", "a");
+		config.setComment("a", "commentA");
+
+		CommentedConfig sub = CommentedConfig.inMemory();
+		sub.set("b", "b");
+		sub.setComment("b", "commentB");
+		config.set("sub", sub);
+		config.setComment("sub", "commentSub");
+
+		assertEquals(config.getComment("a"), "commentA");
+		assertEquals(config.getComment("sub.b"), "commentB");
+		assertEquals(config.getComment("sub"), "commentSub");
+		assertEquals(sub.getComment("b"), "commentB");
+
+		for (CommentedConfig.Entry entry : config.entrySet()) {
+			assertNotNull(entry.getComment());
+		}
+
+		config.clearComments();
+
+		assertNull(config.getComment("a"));
+		assertNull(config.getComment("sub.b"));
+		assertNull(config.getComment("sub"));
+		assertNull(sub.getComment("b"));
+
+		for (CommentedConfig.Entry entry : config.entrySet()) {
+			assertNull(entry.getComment());
+			assertNotNull(entry.getValue());
+		}
+	}
+
+}